As one of the apparatuses to quantitatively analyze particles in a flow cell, a flow cytometer is known, which is arranged such that a fluorescence-labeled sample (cells and particles) is fed into a flow and a laser beam is irradiated onto the flow so that the intensities of scattering light and fluorescence emitted from the sample are measured and the natures of such sample are quantified from such intensities. The fluorescence labeling of the sample, in which specific objects of the cellular surface and interior are labeled, is performed for quantifying the targeted objects and determining the kinds of the cells. Normally, such fluorescence labeling is carried out not only with simple stain, but also with multiple stain. The structural arrangement of one of the conventional apparatus for detecting such multiple stain is shown in FIG. 15. The fluorescence-stained sample 610 forms a flow of such sample within the flow cell 630 with the sample interposed between a sheath solution 620, in which flow the cells (particles) are one by one aligned in one row. The sample 610 is excited with a laser beam 650 so that scattering light and fluorescent light are generated. The fluorescent light is split by a dichroic mirror 660 so as to be selectively detected as its respective kinds through band pass filters 670 matching such respective kinds. A PMT (Photo-Multiplier Tube) 680 and so forth is adopted for a detector. After the detected light components are converted into electric signals (voltage pulses) at the electric signal processing section 640, such signals are numerically expressed so as to be subjected to statistic analysis such as histogram by the software 690 exclusive for such analysis. However, when it is wished that the number of fluorescent color lights to be analyzed by such conventional apparatus be increased, it requires that filter-sets and detectors be incremented thereto, so that such problems happen as the apparatus as a whole becoming large in size and expensive to manufacture and the abatement of fluorescence intensity caused by the dichroic mirror becoming remarkable. Further, when it is wished that a fluorescent color to be analyzed be changed without increasing such color lights, disadvantageously, it requires that a filter-set matching such color change be purchased.
In recent years, the cell function analysis employing fluorochromes capable of measuring an ion concentration of calcium and so forth in a cell prevails over the related field. It is known that as with those fluorochromes, the central wavelength of fluorescence is shifted due to the cellular conditions, the level of pH and temperature thereof, for examples. However, with the above-mentioned apparatus, a fluorescent wavelength band detectable by the same is restricted according to the filter in use and results in being intermittently detected, so that disadvantageously it turns out to be hard to detect the shifting of the central wavelength (peak wavelength) of fluorescence.
The rearrangements of such apparatus are disclosed in Patent Documents 1 and 2. In Patent Document 1, there is disclosure on a microtiter plate reader while in Patent Document 2, there is disclosure on a laser microscope, any of which uses a spectral device such as a diffraction grating and prisms on behalf of the conventional filter-set and a multi detector such as multi PMTS in series and CCDs on behalf of the individual PMTS. Such rearrangement does without purchasing a new filter-set and exchanging the same as well as restrains the fluorescence intensity owing to such filter-set from being abated. Further, when multiple stain measurement is carried out, a wavelength band to be detected can be set in such a band as being invulnerable to crossover of fluorescence. Moreover, since a detection width can be set in a readily manner, the sensitivity also can be freely modified.